1. Field of the Invention
This invention relates to internal combustion engine valvetrain components and, more particularly, to valve rotators.
2. Discussion of the Related Art
Valve rotators are commonly used in some internal combustion engines to provide positive valve rotation during each cycle of an opening phase of engine valve actuation. It is known and appreciated that even slight rotation of a valve during use can increase engine service intervals and extend valvetrain use life by, e.g., minimizing burning and guttering type wear of valves, reducing thermal differentials across each individual valve, reducing carbon buildup on the valves, promoting valve stem lubrication, and/or other benefits.
Known valve rotators are typically classified as being either garter type valve rotators or bearing ball rotators which are commonly referred to as ball type valve rotators. Both garter and ball type valve rotators can be installed in place of a valve spring retainer on the top of a valve spring, or as an additional valvetrain component installed under a valve spring. In either case, whether used as a supplemental valvetrain component, or a replacement component, the valve rotators function by, e.g., utilizing energy associated with valve spring compressive forces and converting such energy into rotational movement of a rotator body within a rotator housing and correspondingly rotating the valve itself.
Typical garter and ball type valve rotators have disadvantages. Garter type valve rotators typically include garter springs of garter type valve rotators are made from relatively small diameter spring material. Correspondingly, the garter springs can have a relatively short use life due to, e.g., exposure to various fatigue forces, loading and unloading at a high rate of recurrence or frequency, temperature cycling between periods of use and non-use, and/or other factors or stresses endured during use. Ball type rotators typically include rigid pockets that hold the bearing balls. In the dynamically changing high stress and load environment in which valve rotators operate, the forces that are applied to the valve rotators are rarely evenly distributed about the rotator body and/or housing, whereby valve rotator bodies and/or housings are subjected to highly localized applications of the input forces. The bearing ball(s) nearest such localized application of force therefore bears relatively more stress of the input force and carry more or even a majority of the load, as compared to the other bearing balls. This can create point loading between such bearing balls and the spring disk with sufficiently great force to create pitting in, or wear grooves into, the spring disk which can shortening its use life.
The applicant's own U.S. Pat. No. 7,997,243 addresses such problems by providing improved ball type valve rotators having multiple ramps that can independently flex with respect to each other to accommodate non-uniform applications of force into the valve rotator.